Re: [PATCH v5 18/18] iommu/arm-smmu-v3: Block ATS for a master upon an ATC invalidation timeout

[sashiko-bot@kernel.org]

> When a CMD_ATC_INV times out, the SMMU stalls at the trailing CMD_SYNC and
> arm_smmu_cmdq_issue_cmdlist() returns -EIO. The CMDQ HW reports the timeout
> on the CMD_SYNC, not the failing CMD_ATC_INV, so the master that caused it
> cannot be identified from the error alone.
> 
> cmds->cmds is sorted by SID, so arm_smmu_cmdq_batch_retry() walks the batch
> and re-issues one CMD_ATC_INV per unique ATS SID; a second -EIO can confirm
> which master is broken. arm_smmu_quarantine_ats() then quarantines it:
>  - clear STE.EATS on every SID it owns
>  - walk master->master_domains marking its INV_TYPE_ATS/_ATS_FULL entries
>    in every domain's invs as INV_TYPE_ATS_BROKEN so later walks skip them
> 
> When a batch carries only one unique Stream ID, the timed-out CMD_SYNC by
> itself identifies the target, in which case quarantine it directly and skip
> the re-issue probes. This is the common case, since it is uncommon for an
> [ ... ]
> when the device's PCIe Completion Timeout expires, which defaults to a
> short interval.
> 
> Assisted-by: Claude:claude-fable-5
> Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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